Erbslöh Aluminium GmbH Heat Transfer Division Filler Metal Flow Barrier Introduction Since the introduction of extruded multiport tubes for the manufacturing of parallel flow condensers in the CAB-process a lot of efforts have been made to reduce the risk of brazing erosion. Brazing erosion Brazing erosion is driven by the fundamental parameters time and temperature {Ref.1}*. On extruded tubes, brazing erosion can be accelerated by preferential filler metal flow from the header to the fins along the longitudinal extrusion lines (Pic. 1). This effect is critical to the essential quality properties, such as burst pressure, pressure cycle resistance and corrosion resistance (Pic. 2). The detection of critical heat exchangers is not guaranteed by the common process control methods. * {Ref.1} Solvay "Filler Metal Management in NOCOLOK Flux Brazing of Aluminum" Pic. 1: Brazing erosion along extrusion lines. Note: Erosion is limited to the area between header and fins. Pic. 2: Filler metal erosion reduces the wall thickness of the outer wall.
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Erbslöh Aluminium GmbH Heat Transfer Division
Filler Metal Flow Barrier
Introduction
Since the introduction of extruded multiport tubes for the manufacturing of parallel flow condensers in the CAB-process a
lot of efforts have been made to reduce the risk of brazing erosion.
Brazing erosion
Brazing erosion is driven by the fundamental parameters time and temperature {Ref.1}*. On extruded tubes, brazing
erosion can be accelerated by preferential filler metal flow from the header to the fins along the longitudinal extrusion
lines (Pic. 1).
This effect is critical to the essential quality properties, such as burst pressure, pressure cycle resistance and corrosion
resistance (Pic. 2). The detection of critical heat exchangers is not guaranteed by the common process control methods.
* {Ref.1} Solvay "Filler Metal Management in NOCOLOK Flux Brazing of Aluminum"
Pic. 1:Brazing erosion along extrusion lines. Note: Erosion is limited to the area between header and fins.
Pic. 2:Filler metal erosion reduces the wall thickness of the outer wall.
Erbslöh Aluminium GmbH Heat Transfer Division
Filler Metal Flow Barrier
Filler Metal Flow Barrier
A new process is introduced by ERBSLÖH to reduce the risk of brazing erosion accelerated by extrusion lines. A fil-
ler metal flow barrier is formed in the space between header and fins (Pic. 4). The filler metal flow barrier (FMFB) is
designed as a groove that is perpendicular to the extrusion lines (EL).
Examples of a post brazed condenser
Note:
• Burst pressure resistance or pressure cycle resistance is not reduced (Pic. 3).
• Internal flow area is not reduced (Pic. 3).
• Corrosion resistance given by a sacrificial zinc layer is not affected (Pic. 5).
• The forming process is chipless and does not affect internal cleanliness.
Advantages
• The groove design and position can be adapted to customers needs.
• Preferential filler metal flow from header to fins is reduced by interruption of extrusion lines. Filler metal fills the gaps and not the fins.
• Quality failure risk (internal/external) is reduced.
• Surface roughness limits can be set to a reasonable level.
• FMFB allows wider brazing window to improve tube-to-header leakage rate.
• No extra costs!
Pic. 3: Example of filler metal flow barrier (cross section.)
Pic. 4: Example of filler metal flow barrier (SEM-top view).
Pic. 5: Zn-element mapping (SEM). Same area as Pic. 4.
Pic. 6a: Example of the effect of the filler metal flow barrier on a post brazed condenser.
Pic. 6b: Detail view of Pic. 6a
EL
FMFB
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